Study Guide: Integumentary System and Skeletal Tissues

Chapter 5 – The Integumentary System

Overview of the Integumentary System

The integumentary system is composed of the skin and its accessory structures, serving as the body's first line of defense and playing roles in protection, sensation, thermoregulation, and more.

• Skin: The largest organ of the body, consisting of multiple layers and associated structures.

• Accessory structures: Hair, nails, glands (sebaceous, sweat, mammary, ceruminous).

Structure of the Skin

• Epidermis: Outermost layer, composed of keratinized stratified squamous epithelium. Provides a tough, protective barrier.

• Dermis: Middle layer, contains connective tissue, blood vessels, nerves, and accessory structures.

• Hypodermis (subcutaneous layer): Deepest layer, composed mainly of loose connective and adipose tissue. Anchors skin to underlying tissues.

Layers of the Epidermis (from superficial to deep)

• Stratum corneum: Dead, keratinized cells; provides waterproof barrier.

• Stratum lucidum: Present only in thick skin (palms, soles); thin, clear layer.

• Stratum granulosum: Cells contain granules; keratinization begins.

• Stratum spinosum: Several layers of keratinocytes; provides strength and flexibility.

• Stratum basale (germinativum): Deepest layer; site of mitosis and new cell production. Contains melanocytes (produce melanin) and Merkel cells (sensory receptors).

Cells of the Epidermis

• Keratinoctyes: Most abundant; produce keratin for protection.

• Melanocytes: Produce melanin pigment, which protects DNA from UV radiation.

• Langerhans (dendritic) cells: Immune defense.

• Merkel (tactile) cells: Sensory receptors for touch.

Dermis Structure

• Papillary layer: Areolar connective tissue; contains dermal papillae (fingerprints).

• Reticular layer: Dense irregular connective tissue; provides strength and elasticity.

Functions of the Integumentary System

• Protection: Physical, chemical, and biological barriers.

• Thermoregulation: Sweat glands and blood flow regulate body temperature.

• Cutaneous sensation: Sensory receptors detect touch, pressure, pain, and temperature.

• Metabolic functions: Synthesis of vitamin D.

• Blood reservoir: Stores blood in dermal vessels.

• Excretion: Eliminates wastes via sweat.

Skin Color

• Melanin: Brown-black pigment produced by melanocytes; protects against UV radiation.

• Carotene: Yellow-orange pigment from diet; accumulates in stratum corneum and fat.

• Hemoglobin: Red pigment in blood; gives skin a pinkish hue.

Clinical correlations: Cyanosis (bluish skin, low oxygen), jaundice (yellow skin, liver dysfunction), erythema (redness, inflammation), pallor (pale, anemia), bronzing (Addison's disease).

Hair and Nails

• Hair: Produced by hair follicles; consists of dead, keratinized cells. Functions in protection, sensation, and thermoregulation.

• Types of hair: Vellus (fine, body hair), terminal (coarse, scalp, eyebrows, etc.).

• Nails: Hard keratin plates protecting the dorsal surface of fingers and toes.

Glands of the Skin

• Sebaceous (oil) glands: Secrete sebum (oil) into hair follicles; lubricates skin and hair, inhibits bacterial growth.

• Sudoriferous (sweat) glands: Two types:

  • Eccrine glands: Widely distributed; produce watery sweat for thermoregulation.

  • Apocrine glands: Found in axillary and genital areas; produce thicker secretion, active at puberty.

• Ceruminous glands: Modified sweat glands in ear canal; produce earwax (cerumen).

• Mammary glands: Modified sweat glands; produce milk.

Skin Disorders and Clinical Conditions

• Acne: Inflammation of sebaceous glands caused by bacterial infection.

• Burns: Classified by depth:

  • First-degree: Epidermis only; redness, pain.

  • Second-degree: Epidermis and part of dermis; blisters.

  • Third-degree: Full thickness; destroys epidermis, dermis, and subcutaneous tissue; requires grafting.

• Skin cancer: Types include basal cell carcinoma, squamous cell carcinoma, and melanoma (most dangerous).

ABCDE Rule for Melanoma

• A: Asymmetry

• B: Border irregularity

• C: Color variation

• D: Diameter > 6 mm

• E: Evolving (change in size, shape, color)

Chapter 6 – Bones and Skeletal Tissues

Types of Cartilage

• Hyaline cartilage: Most abundant; provides support, flexibility, and resilience. Found in articular surfaces, costal cartilage, nose, trachea, larynx.

• Elastic cartilage: Contains elastic fibers; found in external ear and epiglottis.

• Fibrocartilage: Highly compressible; found in intervertebral discs, pubic symphysis, menisci.

Functions of Bones

• Support: Framework for the body.

• Protection: Protects vital organs (e.g., skull, rib cage).

• Movement: Acts as levers for muscles.

• Mineral storage: Stores calcium and phosphate.

• Blood cell formation: Hematopoiesis in red marrow.

• Triglyceride storage: Yellow marrow stores fat.

• Hormone production: Osteocalcin regulates bone formation and energy metabolism.

Bone Structure

• Compact bone: Dense outer layer; provides strength.

• Spongy bone: Internal network (trabeculae); houses red marrow.

Bone Growth and Remodeling

• Appositional growth: Bone increases in diameter by adding new bone to the surface.

• Interstitial growth: Cartilage grows in length at the epiphyseal plate.

Bone Cells

• Osteogenic cells: Stem cells that differentiate into osteoblasts.

• Osteoblasts: Bone-forming cells.

• Osteocytes: Mature bone cells; maintain bone matrix.

• Osteoclasts: Bone-resorbing cells.

Mineral Storage and Homeostasis

• Calcium and phosphate: Main minerals stored in bone; essential for nerve transmission, muscle contraction, and blood clotting.

• Hormonal regulation: Parathyroid hormone (PTH) increases blood calcium by stimulating osteoclasts; calcitonin lowers blood calcium.

Classification of Bones

• Long bones: Longer than wide (e.g., femur, humerus).

• Short bones: Cube-shaped (e.g., carpals, tarsals).

• Flat bones: Thin, flat, slightly curved (e.g., sternum, skull).

• Irregular bones: Complicated shapes (e.g., vertebrae, hip bones).

Table: Types of Cartilage and Their Locations

Type of Cartilage	Main Locations	Key Features
Hyaline	Articular surfaces, costal cartilage, nose, trachea, larynx	Support, flexibility, resilience
Elastic	External ear, epiglottis	Flexible, maintains shape
Fibrocartilage	Intervertebral discs, pubic symphysis, menisci	Strong, resists compression

Additional info:

• Vitamin D is essential for calcium absorption in the intestines.

• Osteoporosis is a condition where bone resorption outpaces bone formation, leading to fragile bones.